The proposed research aims to develop a powerful, flexible power calculation tool to be used for planning group functional magnetic resonance imaging (FMRI) studies. This will require extending the current version of FMRIPower, a software tool under development that is currently listed in the NITRC database. A power calculation requires results from a previous analysis, but flexible models for power analysis increase the ability to find a powerful study design that can be carried out for the lowest cost. The current version of FMRIPower only allows input from the FMRIB Software Library (FSL) and only allows users to alter the number of subjects in the study. By incorporating methods that we have previously developed, we will make FMRIPower accessible to a wider variety of software packages, including the Statistical Parametric Mapping (SPM) and Analysis of Functional NeuroImages (AFNI) packages, and we will extend the power model to allow fluctuations in the number of subjects as well as the number of runs per subject and the number of stimulus events that occur per run. The NITRC website will be helpful in distributing and assessing FMRIPower. The resulting tool will be an asset for the planning of future fMRI studies that will result in better and more cost- effective utilization of research funds, since power analyses help insure the appropriate sample size is collected. PUBLIC HEALTH RELEVANCE: The proposed research aims to improve public health by supplying the means to carry out a flexible power calculation in group fMRI to plan study designs with high enough power to detect an effect, if it is present, while staying within the proposed budget. The current lack of flexible software for calculating power for group fMRI studies often leads investigators to forego power calculation or base sample sizes on power from unrelated studies, leading to studies that are too underpowered to detect an effect or costly overpowered studies. The development of our freely available software tool will allow users of many different fMRI software packages to carry out power analyses with capabilities to make many adjustments to the study design in order to maximize power and minimize cost.